1. Technical Field
Various embodiments of the present disclosure may generally relate to nonvolatile memory devices and, more particularly, to nonvolatile memory (NVM) devices relating to an operation range.
2. Related Art
Semiconductor memory devices are typically categorized as random access memory (RAM) devices or read only memory (ROM) devices according to data volatility thereof. The RAM devices lose stored data when power supplies are interrupted. In contrast, the ROM devices retain stored data when power supplies are interrupted. The ROM devices may also be classified as programmable ROM (PROM) devices or mask ROM devices according to data input methods, that is, data program methods. The PROM devices may be fabricated and distributed without a program and thus are directly programmed by customers (i.e., users) after fabrication thereof. The mask ROM devices may be programmed during fabrication thereof using implantation masks manufactured based on data requested by users. The PROM devices may include one-time PROM (OTPROM) devices, erasable PROM (EPROM) devices and electrically erasable PROM (EEPROM) devices. Once the OTPROM devices are programmed, the programmed data of the OTPROM devices cannot be changed.
N-channel transistors or P-channel transistors may be used as cell transistors of the nonvolatile memory devices, for example, the OTPROM devices. If P-channel transistors are used as the cell transistors of the nonvolatile memory devices, the P-channel cell transistors may have a turn-off status as an initial status thereof and may have a turn-on status as a programmed status thereof. A read operation of the P-channel cell transistors may be executed by sensing a voltage level of a bit line connected to any one selected from the P-channel cell transistors. In such a case, the voltage level of the bit line may be determined by a resistance ratio of a resistance value of a load resistor coupled between a supply voltage line and the bit line and an equivalent resistance of the selected P-channel cell transistor. As electronic systems are scaled down and classified into more diverse systems, more supply voltage levels are required to operate the nonvolatile memory devices employed in the electronic systems. In such cases, the read operation of the nonvolatile memory devices employing the P-channel transistors as the cell transistors may be unstably executed. As a result, an operation range of the nonvolatile memory devices may be limited according to a magnitude of the supply voltage.